Unless you apply database foreign key constraints extensively, it is
possible to end up with orphaned keys in your database. For example,
suppose Magazine m has a
reference to Article a. If you
delete a without nulling m's
reference, m's database record will wind up with
an orphaned key to the non-existent a record.
![[Note]](img/note.gif) | Note |
|---|---|
One way of avoiding orphaned keys is to use dependent fields. |
Kodo's
kodo.OrphanedKeyAction configuration property controls
what action to take when Kodo encounters an orphaned key. You can set
this plugin string (see Section 2.5, “Plugin Configuration”) to
a custom implementation of the
kodo.event.OrphanedKeyAction interface, or use
one of the built-in options:
log: This is the default setting. This option logs a message for each orphaned key. It is an alias for thekodo.event.LogOrphanedKeyActionclass, which has the following additional properties:Channel: The channel to log to. Defaults tokodo.Runtime.Level: The level to log at. Defaults toWARN.
exception: Throw an exception when Kodo discovers an orphaned key. This is an alias for thekodo.event.ExceptionOrphanedKeyActionclass.In JPA, the exception type will be
javax.persistence.EntityNotFoundException.In JDO, the exception type will be
javax.jdo.JDOObjectNotFoundException.none: Ignore orphaned keys. This is an alias for thekodo.event.NoneOrphanedKeyActionclass.